The invention relates to a catheter having a ballon.
In the medical field, especially in radiology and cardiology, the expansion (dilatation) of constrictions (stenoses) along the arteries is currently a frequently used and highly satisfactory method of increasing the blood flow, and thus the supply of oxygen and energy, to the peripheral vascular system.
Here, a so-called dilatation catheter is pushed to the appropriate, stenosed blood vessel segment where the balloon at the leading end is expanded.
A frequent complication of the expansion of blood vessel constrictions is the formation of thrombi in the blood vessels. This often has severe consequences for the patient, especially in the region of the heart, and the difficulties will be described below with particular reference to the coronary situation.
To mitigate the above complication, various medications including, among others, dissolving agents which are to redissolve the thrombi, are dispensed via an intracoronary route (proximal and distal to the balloon) during, before and after the expansion. However, at the time of the actual expansion and the intracoronary thrombus formation induced by the same under certain circumstances, the expanded balloon prevents these medications from penetrating to the desired location. The medications can actually arrive at the dilatation area only after the balloon has been contracted or withdrawn from the expanded region of the stenosis. Under certain circumstances, however, this can be too late for effective action.
Thrombi which have formed in the area of dissections, for example, can readily cause an embolism in the peripheral system or be the starting point for a spontaneous thrombotic blockage. Also, lesions can increase the susceptibility of the inner blood vessel layer to coagulum formation.
The German Offenlegungsschrift 32 35 974 discloses a catheter which can deliver medications to the region of a stenosis during the dwell time of the catheter. Here, expandable balloons are disposed on either side of a stenosis and bound the area of the stenosis from the front and the back. A medication is then delivered to the region between the balloons via openings in the catheter wall. A disadvantage is that the medication can act only while the catheter is in the blood vessel which requires long dwell times with associated drawbacks. Penetration of the medication into the wall itself is very unsatisfactory because, as a rule, the blood vessel wall is undamaged. Hence, active metabolic and diffusion processes, which require relatively long times, have been contemplated. This is disadvantageous particularly since a catheter can quasi-block the blood vessel for only a relatively short period, e.g., seconds to at most a few minutes. However, it is questionable whether the catheter of the German Offenlegungsschrift 32 35 974 can provide an effective treatment within this short interval.
U.S. Pat. No. 4,423,725 also shows an arrangement having a plurality of balloons. Two of the balloons can be expanded on either side of a location to be treated and then seal the zone between the balloons. In addition, a third balloon is provided intermediate the sealing balloons and contains a medicinal active substance which can be dispensed in the zone between the sealing balloons.
To this end, flow apertures are distributed over the surface of the middle balloon, and the active substance can exit through the flow apertures to arrive, for the most part, in the intermediate zone between the two outer balloons. Here, also, penetration of the medication directly into the blood vessel wall during delivery of the active substance is inadequate and an extended dwell time of the catheter is therefore required to achieve penetration by diffusion and the like. Moreover, the structure of this balloon catheter, which contains three individual balloons, is complicated.
Finally, an implantable medication carrier, which is designed to deliver an active substance over an extended period of time, is known from U.S. Pat. No. 3,279,996. This medication carrier includes a capsular body having a porous outer wall through which the active substance can slowly diffuse. Delivery of the active substance within a short time span is neither contemplated nor possible here.
It is an object of the invention to create a catheter of the type indicated at the outset which makes it possible to medicinally treat the dilated blood vessel region which the balloon is expanded. The required dwell time of the catheter for effective treatment is to be substantially reduced. Moreover, the range of applications of the catheter is to be increased and it is to be usable for the treatment of hollow organs also.
To achieve this object, it is proposed that the longitudinal ends of the balloon be provided with sealing zones next to a central region and at the outer side of the balloon which is intended to contact the hollow organ, and that the pores or the like be arranged in the central region with spacing from the ends of the balloon.
A balloon catheter in which the balloon wall is provided with openings in the region of heating zones is already known from the German patent 35 16 830. However, these openings serve for irrigation of the balloon and are to prevent tissue from sticking to the balloon. Furthermore, blood is to be completely expelled from the area between the balloon wall and the blood vessel wall by means of the openings.
This catheter is neither intended nor suited for targeted infiltration or "pressing" of a medicinal active substance into a predetermined treatment zone. Per the intended use, the openings in the balloon wall are specifically arranged to irrigate the intermediate region between balloon and tissue However, this is possible only during a thermal treatment where contact with the tissue just exists but not where an appropriate pressure is applied during expansion of the stenosis.
In contrast, the invention makes it possible for specific wall segments of a blood vessel or hollow organ to be enriched with an active substance. This enrichment already takes place upon dilatation by infiltration of the wall under pressure. During dilatation, smaller and larger pores, tears, lesions and even dissections open up or are forcefully formed in the inner wall of the blood vessel since part of the lumen is expanded by a multiple upon dilatation and the inner wall of the blood vessel can only withstand this process to a limited extent. Immediately following dilatation, such artificially created openings in the wall--due to mechanical-elastic restoring forces--can partially reclose.
In this manner, the action of highly effective medications can be developed at a precise time, and thus optimally, so that side effects during the expansion of blood vessel constrictions and the like can be markedly reduced. The disposition of the pores in the central region and at a distance from the ends of the balloon creates sealing zones adjacent the stenosis to the front and back of the latter. The sealing zones can largely prevent the active substance leaving the central region of the balloon from flowing off to the sides in an undesired fashion. This also prevents a pressure drop which would affect penetration of the active substance into the tissue to the degree contemplated here.
Due to mechanical expansion of the stenosis to the point where dissections form, the tissue opens so that the active substance can be forced in within a short period. In a manner somewhat comparable to an injection, a depot for the active substance is created in the tissue and makes it possible to achieve an active period essentially equal to the dwell time of the catheter. This, in turn, provides the substantial advantage, especially in the coronary region, that occlusion of the blood vessel during dilatation can be eliminated within a very short period.
Active substances are here understood to mean primarily those medications which are capable of dissolving fresh thrombi with varying degrees of efficiency (so-called thrombolytics or dissolving agents) and/or are capable of preventing a new blockage for moderate and long periods of time.
The active substance can further be a substance selected from the group of fibrin adhesives which "cement" tears in the intima or media of the artery by means of local coagulation processes. This avoids the possible consequences associated with the formation of a false lumen and the formation of a thrombus by contact between the deeper exposed wall structures and the blood. Moreover, the use of many medications (nitro, Ca.sup.++-antagonists, etc.) which are effective in blood vessels is contemplated. Good medicinal treatment of hollow organs such as, for example, bladder, gall bladder, stomach, intestine, ureter, bronchi and the like, is likewise possible with the balloon catheter of the invention. Here, also, the active substance can be applied directly to the location to be treated.
In an embodiment where the wall of the balloon is provided with a plurality of pore-like through apertures and the active substance to be applied is disposed inside the balloon, the dilating medium expediently contains the medication or the like to be applied or itself constitutes this medication.
The active substance can therefore travel through the wall of the balloon during dilatation directly to the inner wall of the blood vessel or hollow organ.
According to another embodiment, one or more compartments for the active substance can be provided internally in the region of the balloon wall. The compartments have pore-like apertures opening to the outside and are sealed on the inside.
Upon dilatation, the active substance in the compartments is delivered to the exterior due to the pressure increase within the balloon and thus arrives at the inner wall of the blood vessel or hollow organ in the desired fashion.
A further embodiment of the invention has a plurality of compartments which are sealed from one another with neighboring compartments accommodating different active components.
On the one hand, this allows a plurality of different active substances to be stored and then dispensed during expansion. When using adhesive, it also becomes possible to employ multicomponent adhesives. Here, the different components are stored in alternating individual compartments and are only combined and activated upon issuing during dilatation.
In another embodiment, the outer side of the balloon carries a porous, sponge-like layer which is located between the sealing zones, contains an active substance and can be at least partially compressed when urged against the wall of the blood vessel or hollow organ. The active substance is then liberated from the outer layer upon pressing of the latter against the inner wall of the blood vessel or hollow organ and, in particular, is thus liberated in the region of the greatest counterpressure.
A urine catheter having a sponge-like, expandable zone is known from the German Offenlegungsschrift 23 11 087. However, this sponge-like zone functions to fix the catheter when the sponge-like zone is contacted by liquid and also functions to create a blockage capable of inhibiting infections which occur. This catheter is not suited for the introduction of medications into the blood vessel wall or for the deposition of medications, which are subsequently forced into the blood vessel wall by expansion, in the sponge.
According to yet a further embodiment of the invention, the exterior of the balloon is provided with a separable annular layer which preferably can bind to the inner wall of the blood vessel or hollow organ and contains the active substance. Upon dilatation, the annular layer is pressed against the inner wall of the blood vessel or hollow organ and, under appropriate circumstances, adheres thereto. When the balloon is collapsed, the outer skin of the balloon and the annular layer are separated so that the balloon can be withdrawn. The annular layer remains in the treatment zone and can release its active substance there.
In an expedient additional embodiment, the annular layer and the like consists of resorbable material. This has the advantage that no foreign bodies remain, e.g., in the coronary system, for an extended eriod and that the tunnel-like structure implanted in the artery or the like is destroyed after some time and is then no longer present. In this manner, foreign body complications are avoided.